An experiment was conducted to determine the effect of supplementing a reduced crude protein (CP) diet with apple pomace on the ammonia emissions from growing pig rooms. Four pigs (45 kg BW) each were assigned to one of two diets. Each group was housed in a separate room and fed a standard diet (CP 16.6%) or a low CP, amino acidsupplemented diet (CP 9.1%) containing 23.1% of dried apple pomace for two 7-day experimental periods. After the completion of the first period, the pigs were switched to the other diet. The daily ammonia emissions, measured for 3 days after a 4-day adaptation period, were much lower for pigs fed the apple pomace-supplemented diet than for pigs fed the standard diet (0.47 g/pig vs 7.30 g/pig, respectively). The daily nitrogen intake for the standard diet and the apple pomace-supplemented diet was 58.1 and 35.5 g/pig, respectively. The pigs fed the apple pomace-supplemented diet excreted more fecal nitrogen than pigs fed the standard diet (17.5 g/day vs 11.0 g/day, respectively), but urinary nitrogen excretion with the apple pomace-supplemented diet was estimated to be 2.9 g/day, which was much lower than that for the standard diet (27.0 g/day). The addition of apple pomace to a reduced CP, amino acid-supplemented diet reduces urinary nitrogen excretion and thereby ammonia emission.